Quantum mechanics tells us that certain unobserved physical systems can have odd behavior. A particle which is decoupled from its environment and which has two possible states will not necessarily be in either of those states, until observed. Putting this in quantum mechanical terms, the particle is simultaneously in a "superposition" of both of those states. However, this only applies while the particle is in certain conditions--decoupled from its environment. Any attempt to actually observe the particle couples the particle to its environment, and hence causes the particle to default into one or the other of the eigenstates of the observable operator.
This behavior is part of the superposition principle. The "superposition principle" is illustrated by a famous hypothetical experiment, called the cat paradox. a cat in a box with a vial of poison. The vial containing the poison could equally likely be opened or not opened. If the box/cat/poison is decoupled from its environment, then the cat achieves a state where it is simultaneously dead and not dead. However, any attempt to observe the cat, causes the system to default to dead or alive.
The theory of quantum mechanics predicts that N particles can also exist in such superposition states.
Lithography is a process of etching features on a substrate. Photolithography uses light to etch these features. Each spot can be etched, or not etched, to form a desired feature. In general, it is desirable to make the features as small as possible.
In the prior art, called Classical Optical Interferometric Lithography, a lithographic pattern is etched on a photosensitive material using a combination of phase shifters, substrate rotators, and a Mach-Zehnder or other optical interferometer. The minimum sized feature that can be produced in this fashion is on the order of one-quarter of the optical wavelength [Brueck 98]. The only way to improve on this resolution classically is to decrease the physical wavelength of the light used in the etching process.
This can come at a tremendous commercial expense. Optical sources and imaging elements are not readily available at very short wavelengths, such as hard UV or soft x ray.